JPH02299329A - Monitoring method for optical repeater - Google Patents

Abstract

PURPOSE:To attain the monitor through the use of a function built in an existing repeater without using a VCO and to reduce the circuit scale by detecting a mean voltage from a modulated signal and monitoring the optical input level of an optical repeater. CONSTITUTION:When a fault takes place in a signal inputted to other terminal station, a test signal is sent at first from the terminal equipment and a repeater near a transmission terminal state side is monitored sequentially. When a repeater detects a signal to be a test signal for its own equipment, a switch SW 1 is closed to form a monitoring loop and the signal is inputted to one input of an exclusive OR circuit 250 to apply the modulation with the inversion/ noninversion, and the output is returned to a terminal station 21 via an outgoing line. The terminal station 21 processes the returned signal to extract a DC component via a low pass filter 232. The relation between the optical input level and the mean voltage is obtained in advance to monitor the optical input level. Thus, the input level of the light is monitored.

Description

[Detailed Description of the Invention] [Summary] This article relates to a method for monitoring optical repeaters used in optical communications, especially optical repeaters that use a DC/DC converter as an automatic gain adjustment function to compensate for fluctuations. The purpose of the present invention is to provide a monitoring method that makes it possible to monitor a repeater using existing functions within the repeater without using a Therefore, the output of a pulse width modulation circuit that outputs a signal with a different pulse width applies inverted or non-inverted modulation to the optical-to-electrical converted signal by the light receiving means, and the average voltage is detected from the modulated signal. The optical repeater is configured to monitor the optical input level to the optical repeater.

[Industrial application field]

The present invention relates to an optical repeater used in optical communications, and particularly to a method for monitoring an optical repeater that uses a DC/DC converter as an automatic gain adjustment function to compensate for sensitivity fluctuations.

Figure 4 shows an optical communication system. In optical communications, when transmitting a signal from one terminal station to another, the optical signal propagating through the transmission path suffers loss and waveform distortion, so optical repeaters are required to compensate for these losses. The repeater is composed of an optical-to-electrical conversion circuit (light receiving means), an amplifier circuit, an identification circuit, and the like.

The unique part of these optical repeaters is the optical-to-electrical conversion.
Automatic gain adjustment (hereinafter referred to as AG) to compensate for sensitivity fluctuations
(abbreviated as C) function.

In optical communication using such optical repeaters, if an abnormality occurs such as the receiver not being able to receive a normal signal, it is possible to manually monitor each repeater to see if it is receiving a normal level of optical signal. It is necessary to maintain the transmission line or repeater.

[Prior Art] An example of the configuration of a conventional optical repeater is shown in FIG. In the figure, 31 is a relay function on the uplink side, and 32 is a relay function on the downlink side. The two relay functions have the same configuration.

Normally, a signal is optical-to-electrically converted by the light receiving means 310 while the bias voltage is adjusted by the DC/DC converter 312. After the signal is amplified and waveform-shaped by the amplifying/discriminating means 311, the signal is converted from electric to optical by the LD 315. being sent.

We will explain what happens during maintenance, such as when a signal cannot be received normally at the receiving terminal station.

A test signal is transmitted from the transmitting terminal station. When the control unit 316 detects a test signal, the optical-to-electrical converted signal is modulated by the output of a voltage controlled oscillator (hereinafter abbreviated as VCO) 313 that generates a signal with a frequency corresponding to the bias voltage of the light receiving unit 310. In step 317, the signal is subjected to inverted/non-inverted modulation and sent back to the terminal station by the relay function on the downlink side.

The bias voltage of the light receiving means 310 and the frequency of the VCO 313 are in a proportional relationship. Furthermore, there is a relationship as shown in FIG. 3 between the light input level to the light receiving means 310 and the bias voltage.

Therefore, a similar relationship exists between the frequency and the optical input level.

Therefore, the terminal station monitors the optical input level from the returned signal. When it is determined that the optical input level is normal, the next repeater is monitored to detect the fault and perform maintenance.

[Problems to be Solved by the Invention] When monitoring a repeater as described above, the light receiving means 31 is used as a signal to modulate the optical-to-electrical converted signal.
VCO313 that performs V/F conversion according to the bias voltage of 0
are using. This increases the circuit scale of the repeater. Further, problems such as increased power consumption have arisen.

Therefore, an object of the present invention is to provide a monitoring method that makes it possible to monitor a repeater using existing functions within the repeater without using CO.

[Means to solve the problem]

FIG. 1 shows the principle configuration diagram of the present invention. The present invention particularly relates to an optical repeater that uses a DC/DC converter as an automatic gain adjustment function.

In order to achieve the above-mentioned object, the present invention provides a circuit in the DC/DC converter 3 that outputs a signal by changing the pulse width in order to compensate for sensitivity fluctuations of the light receiving means 1.

By the output of the pulse width modulation circuit (hereinafter abbreviated as PWM) 31, the signal is inverted into an optical-to-electrical converted signal by the light receiving means 1;
The optical repeater is configured to perform non-inverting modulation and detect the average voltage from the modulated signal to monitor the optical input level to the optical repeater.

[Effect]

By the means, the PW in the DC/DC converter 3
A signal obtained by modulating the optical-to-electrical converted signal with an output signal having a pulse width proportional to the bias voltage of the light receiving means 1 of M31 is extracted, and a signal whose pulse width is proportional to the bias voltage of the light receiving means 1 is extracted by the extracted signal. Detect voltage value.

Furthermore, since the optical input level and the bias voltage are proportional, it is possible to monitor the optical input level to the optical repeater based on the voltage value. Therefore, it is possible to monitor repeaters using existing functions without using cO.

〔Example 〕

A configuration diagram of an embodiment of the present invention is shown in FIG. In the figure, an avalanche photodiode (hereinafter abbreviated as APD) 251 corresponds to the light receiving means 1 of FIG. 1, and an exclusive OR circuit (hereinafter abbreviated as EX-OR circuit) 250 corresponds to the modulating means 4 of FIG. In addition, when the monitoring unit 259 detects that the optical-to-electrical converted signal, which has been amplified and waveform-shaped, is a test signal when an abnormality occurs and is addressed to the own repeater, it controls the switch SWI to be in the ON state. . Monitoring unit 269 and switch SW
I is a control unit for detecting a test signal transmitted when a failure occurs and forming a monitoring loop. Embodiments will be described in detail below with reference to the drawings.

When normal optical communication is being performed, the switch SWI is controlled to be in the off state. Then, a signal transmitted from the transmitter 22 in the terminal station 21 is amplified and regenerated by each repeater and transmitted to the other terminal station. APD2 inside the repeater
51 bias voltage is DC/DC converter 254
adjusted by. This adjustment detects the voltage of the photo-electrically converted signal, outputs a signal with a pulse width corresponding to the voltage using PWM 255, and controls the transistor on/off to adjust the bias voltage, thereby changing the sensitivity. Compensation is being provided. Therefore, the bias voltage and pulse width are in a proportional relationship.

Next, maintenance when an abnormality occurs will be explained. Here, a case will be explained in which an abnormality occurs in the uplink.

If an abnormality occurs in the signal input to the other terminal station, first a special test signal is transmitted from the terminal station. In this case, an address signal indicating which repeater the signal is directed to is superimposed at the beginning of the signal. Then, monitoring is performed in order from the repeater closest to the transmitting terminal station. In the repeater, when the monitoring unit 259 detects that it is a test signal to the own device, the SWI
A monitoring loop is formed by turning on. In this embodiment, the test signal is a series of signals having a low mark rate of about 1/4. For example (1000100010
001000...) Q These signals are subjected to optical-to-electrical conversion, amplification and waveform shaping, and an exclusive OR (hereinafter abbreviated as EX-OR) circuit 25 serves as an inverting/non-inverting modulation means.
Enter one of 0. The output of the PWM 255 is input to the other terminal of the EX-OR circuit 250. In this EX-OR circuit 250, PWM2 is applied to the optical-electrical converted signal.
Inversion/non-inversion modulation is applied depending on the pulse width of the output signal of 55, and a signal with a mark rate of 1/4 or 3/4 is output depending on the pulse width.

The output is electrically-optically converted by a light-emitting diode (hereinafter abbreviated as LD) 268 via a drive circuit 267 on the downlink side 26 and sent back to the transmitting terminal station 21.

At the terminal station, the returned signal is subjected to normal reception processing such as optical-to-electrical conversion by a receiving circuit 233, and then passed through a low-pass filter (hereinafter abbreviated as LPF) 232 to convert the DC component (average voltage ) will be extracted. As described above, the bias voltage and the pulse width of the output signal of the PWM 255 are in a proportional relationship. Furthermore, the pulse width and the average voltage detected at the terminal station are also in a proportional relationship. Therefore, the average voltage and bias voltage are also in a proportional relationship. Further, there is a relationship between the bias voltage and the optical input level as shown in FIG. Therefore, a similar relationship exists between the average voltage and the optical input level. Therefore, by determining the relationship between the optical input level and the average voltage in advance in a normal state, monitoring the average voltage means monitoring the optical input level.

If the average voltage is abnormally high, that is, the optical input level is abnormally low, it means that an abnormality has occurred in the transmission path to the repeater currently being monitored.

Furthermore, if the optical input level there is normal, by monitoring the next repeater, an abnormal location can be detected and maintenance can be carried out.

The present invention has been described above according to the embodiments. In this embodiment, the mark rate was set to 1/4 as the test signal, but the effect remains the same if the mark rate is not 1/2. be.

〔Effect of the invention 〕

According to the present invention, it is possible to provide a monitoring method that makes it possible to monitor a repeater using existing functions within the repeater without using a VCO, thereby reducing the circuit scale.

[Brief explanation of drawings]

Figure 1 is a diagram showing the principle of the present invention, Figure 2 is a diagram showing the configuration of an embodiment of the present invention, Figure 3 is a diagram showing the relationship between optical input level and bias voltage, and Figure 4 is a diagram of a conventional optical repeater. Block diagram: FIG. 5 is a diagram showing an optical communication system. In the figure: 1... Light receiving means 2... Amplifying/discriminating means 3... DC/DC converter 4... Modulating means 31... Pulse width modulation circuit Principle configuration diagram of the present invention. Diagram 3 showing the first open system of current and bias voltage
Diagram of the light of night, composition of mesopteran organs 4 times

Claims (1)

[Scope of Claims] In an optical repeater monitoring system that uses a DC/DC converter as an automatic gain function for compensating for sensitivity fluctuations of a light receiving means of an optical repeater, the DC/DC converter (3) includes: , the light receiving means (
The output of the pulse width modulation circuit (31) which outputs a signal by changing the pulse width in order to compensate for sensitivity fluctuations in step 1) inverts and non-inverts the signal optically-electrically converted by the light receiving means (1). 1. A method for monitoring an optical repeater, comprising: monitoring an optical input level to the optical repeater by multiplying the modulated signal by detecting an average voltage from the modulated signal.